Apparatus and method for encoding and decoding TFCI in a mobile communication system

ABSTRACT

Disclosed is an apparatus for encoding k consecutive inputs indicating a TFCI (Transport Format Combination Indicator) of each of successively transmitted frames into a sequence of m symbols in an NB-TDD (Narrowband-Time Division Duplex) mobile communication system. An encoder encodes the k input bits into a sequence of at least 2 n  symbols where 2 n &gt;m, using an extended Reed-Muller code from a Kasami sequence. A puncturer performs puncturing on the sequence of 2 n  symbols from the encoder so as to output a sequence of m symbols.

PRIORITY

[0001] This application claims priority to an application entitled“Apparatus and Method for Encoding and Decoding TFCI in a MobileCommunication System” filed in the Korean Industrial Property Office onJun. 12, 2000 and assigned Ser. No. 2000-33107, the contents of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to an apparatus andmethod for a TFCI (Transport Format Combination Indicator) codegenerator in a CDMA mobile communication system, and in particular, toan apparatus and method for encoding a TFCI in an NB-TDD(Narrowband-Time Division Duplex) mobile communication system.

[0004] 2. Description of the Related Art

[0005] In general, a CDMA mobile communication system (or an IMT-2000system) transmits data frames of various services such as a voiceservice, an image service and a data service all together, using asingle physical channel. Such service frames are transmitted at either afixed data rate or a variable data rate. As for the different servicestransmitted at a fixed data rate, it is not necessary to inform areceiver of a spreading rate of the respective service frames. However,regarding the services transmitted at a variable data rate, it isnecessary to inform the receiver of a spreading rate of the respectiveservice frames. In the IMT-2000 system, the data rate is in inverseproportion to the data spreading rate.

[0006] When the respective services use different frame transfer rates,a TFCI is used to indicate a combination of the currently transmittedservices. The TFCI secures correct reception of the respective services.

[0007]FIG. 1 illustrates an example in which an NB-TDD communicationsystem uses the TFCI. Herein, the NB-TDD system employs 8PSK (8-aryPhase Shift Keying) modulation for high-speed transmission, and the TFCIbits are encoded to a code of length 48 before transmission. As shown inFIG. 1, one frame is divided into two sub-frames of a sub-frame#1 and asub-frame#2. Each sub-frame is comprised of 7 time slots TS#0-TS#6.Among the 7 time slots, the odd-numbered time slots TS#0, TS#2, TS#4 andTS#6 are used for an uplink transmitted from a mobile station to a basestation, while the even-numbered time slots TS#1, TS#3 and TS#5 are usedfor a downlink transmitted from a base station to a mobile station. Eachtime slot has a structure in which data symbols, a first part of TFCI, amidamble signal, SS symbols, TPC symbols, a second part of TFCI, datasymbols and GP are sequentially time-multiplexed.

[0008]FIG. 2 illustrates a structure of a transmitter for transmitting aframe in a conventional NB-TDD communication system. Referring to FIG.2, a TFCI encoder 200 encodes an input TFCI and outputs a TFCI symbols.A first multiplexer (MUX) 210 multiplexes the TFCI symbols output fromthe TFCI encoder 200 and other signals. Here, the “other signals” referto the data symbol, the SS symbol and the TCP symbol included in eachslot of FIG. 1. That is, the first multiplexer 210 multiplexes the TFCIsymbol and the other signals except for the midamble signal of FIG. 1. Achannel spreader 220 channel-spreads the output of the first multiplexer210 by multiplying it by a given orthogonal code. A scrambler 230scrambles the output of the channel spreader 220 by multiplying it by ascrambling code. A second multiplexer 240 multiplexes the output of thescrambler 230 and the midamble signal as shown in FIG. 1. Here, thefirst multiplexer 210 and the second multiplexer 240 generate the framestructure of FIG. 1, under the control of a controller (not shown).

[0009]FIG. 3 illustrates a structure of a receiver in the conventionalNB-TDD communication system. Referring to FIG. 3, a first demultiplexer340 demultiplexes an input frame signal under the control of acontroller (not shown), and outputs a midamble signal and other signals.Here, the “other signals” include the TFCI symbol, the data symbol, theSS symbol and the TCP symbol. A descrambler 330 descrambles the othersignals output from the demultiplexer 340 by multiplying them by ascrambling code. A channel despreader 320 channel-despreads the outputof the descrambler 330 by multiplying it by an orthogonal code. A seconddemultiplexer 310 demultiplexes the signals output from the channeldespreader 320 into the TFCI symbol and other signals, under the controlof the controller. Here, the “other signals” include the data symbol,the SS symbol, and the TCP symbol. A TFCI decoder 300 decodes the TFCIsymbol output from the second demultiplexer 310 and outputs TFCI bits.

[0010] The TFCI is comprised of 1 to 2 bits to indicate 1 to 4combinations of the services, comprised of 3 to 5 bits to indicate 8 to32 combinations of the services, or comprised of 6 to 10 bits toindicate 64 to 1024 combinations of the services. Since the TFCI isinformation indispensable when the receiver analyzes the respectiveservice frames, a transmission error of the TFCI may prevent thereceiver from correctly analyzing the respective service frames.Therefore, the TFCI is encoded using an error correcting code so thateven though a transmission error occurs on the TFCI, the receiver cancorrect the error.

[0011]FIG. 4 illustrates a scheme for encoding the TFCI using an errorcorrecting code according to the prior art. Referring to FIG. 4, anextended Reed-Muller encoder 400 encodes an input 10-bit TFCI andoutputs a 32-symbol TFCI codeword. A repeater 410 outputs intacteven-numbered symbols of the TFCI codeword output from the extendedReed-Muller encoder 400 and repeats odd-numbered symbols, therebyoutputting a total of 48 coded symbols. In FIG. 4, a less-than-10-bitTFCI is constructed to have a 10-bit format by padding a value of 0 fromthe MSB (Most Significant Bit), i.e., from the leftmost bit. The (32,10) extended Reed-Muller encoder 400 is disclosed in detail in Koreanpatent application No. 1999-27932, the contents of which are herebyincorporated by reference.

[0012] In the (32, 10) extended Reed-Muller encoder 400, a minimumdistance between codes is 12. After repetition, an input code isconverted to a (48, 10) code having a minimum distance of 16. Ingeneral, an error correction capability of binary linear codes isdetermined depending on the minimum distance between the binary linearcodes. The minimum distance (dmin) between the binary linear codes tobecome optimal codes is disclosed in a paper entitled “An Updated Tableof Minimum-Distance Bounds for Binary Linear Codes” (A. E. Brouwer andTom Verhoeff, IEEE Transactions on information Theory, VOL 39, NO. 2,MARCH 1993).

[0013] The paper discloses that the minimum distance required for thebinary linear codes used to obtain a 48-bit output from a 10-bit inputis 19 to 20. However, since the encoder 400 has a minimum distance of16, the error correction encoding scheme of FIG. 4 does not have optimalcodes, causing an increase in TFCI error probability in the same channelenvironment. Because of the TFCI error, the receiver may misjudge a rateof the data frame and decode the data frame at the misjudged rate,thereby increasing a frame error rate (FER). Therefore, it is importantto minimize a frame error rate of the error correction encoder forencoding the TFCI.

SUMMARY OF THE INVENTION

[0014] It is, therefore, an object of the present invention to provide a(48, 10) encoding and decoding apparatus and method for encoding a TFCI.

[0015] It is another object of the present invention to provide anapparatus and method for encoding a TFCI in an NB-TDD CDMA mobilecommunication system.

[0016] It is further another object of the present invention to providean apparatus and method for decoding a TFCI in an NB-TDD CDMA mobilecommunication system.

[0017] To achieve the above and other objects, there is provided anapparatus for encoding k consecutive inputs indicating a TFCI of each ofsuccessively transmitted frames into a sequence of m symbols in anNB-TDD mobile communication system. An encoder encodes the k input bitsinto a sequence of at least 2^(n) symbols where 2^(n)>m, using anextended Reed-Muller code from a Kasami sequence. A puncturer performspuncturing on the sequence of 2^(n) symbols from the encoder so as tooutput a sequence of m symbols.

[0018] Preferably, the encoder comprises: a 1-bit generator forgenerating a sequence of same symbols; a base orthogonal sequencegenerator for generating a plurality of base orthogonal sequences; abase mask sequence generator for generating a plurality of base masksequences; and an operator for receiving the TFCI including a firstinformation part indicating conversion to a biorthogonal sequence, asecond information part indicating conversion to an orthogonal sequenceand a third information part indicating conversion to a mask sequence.The operator is also for generating the sequence of 2^(n) symbols bycombining an orthogonal sequence selected from the base orthogonalsequences by the second information part, a biorthogonal sequenceconstructed by a combination of the selected orthogonal sequence and thesame symbols selected by the first information part, and a mask sequenceselected by the third information part.

[0019] Preferably, the operator comprises a first multiplier formultiplying the same symbols by the first information part; a pluralityof second multipliers for multiplying the base orthogonal sequences byTFCI bits constituting the second information part; a plurality of thirdmultipliers for multiplying the base mask sequences by TFCI bitsconstituting the third information part; and an adder for generating thesequence of 2^(n) symbols by adding outputs of the first to thirdmultipliers.

[0020] To achieve the above and other objects, there is provided anmethod for encoding 10 consecutive input bits indicating a TFCI of eachof successively transmitted frames into a sequence of 48 coded symbolsin an NB-TDD mobile communication system, comprising: creating firstsequences having a length 48 punctured orthogonal sequences; creatingsecond sequences having a length 48 punctured mask sequences;multiplying the first sequences with each associated TFCI bit and thesecond sequences with each associated TFCI bit; and adding the eachresulting sequences calculated by the multiplication and outputting thesequence of 48 symbols wherein the punctured orthogonal sequences andthe punctured mask sequences are sequences generated by puncturingfollowing positions out of length 64 Walsh codes and length 64 masks;{0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

[0022]FIG. 1 is a diagram illustrating a frame format used in aconventional NB-TDD CDMA communication system;

[0023]FIG. 2 is a diagram illustrating a structure of a transmitter fortransmitting a frame in the conventional NB-TDD communication system;

[0024]FIG. 3 is a diagram illustrating a structure of a receiver for theconventional NB-TDD communication system;

[0025]FIG. 4 is a diagram illustrating a scheme for encoding a TFCIusing an error correcting code according to the prior art;

[0026]FIG. 5 is a diagram illustrating a scheme for encoding a linearerror correcting code;

[0027]FIG. 6 is a flow chart illustrating a procedure for creating amask function using a Kasami sequence family;

[0028]FIG. 7A is a diagram illustrating an apparatus for encoding a TFCIaccording to a first embodiment of the present invention;

[0029]FIG. 7B is a diagram illustrating an apparatus for encoding a TFCIaccording to a second embodiment of the present invention;

[0030]FIG. 8 is a flow chart illustrating an operation performed by theencoder of FIG. 7A;

[0031]FIG. 9 is a diagram illustrating an apparatus for decoding a TFCIaccording to an embodiment of the present invention;

[0032]FIG. 10 is a flow chart illustrating an operation performed by thecomparator shown in FIG. 9;

[0033]FIG. 11 is a diagram illustrating a structure of 1024 codes outputfrom a (64, 10) encoder according to an embodiment of the presentinvention; and

[0034]FIG. 12 is a flow chart illustrating an operation performed by theencoder of FIG. 7B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0035] A preferred embodiment of the present invention will be describedherein below with reference to the accompanying drawings. In thefollowing description, well-known functions or constructions are notdescribed in detail since they would obscure the invention inunnecessary detail.

[0036] A CDMA mobile communication system according an embodiment of thepresent invention uses extended Reed-Muller codes to create optimalcodes when encoding a TFCI. Commonly, a measure, i.e., a parameterindicating performance of a linear error correcting code, includesdistribution of a Hamming distance of a codeword of an error correctingcode. The Hamming distance refers to the number of non-zero symbols inthe respective codewords. That is, for a codeword ‘0111’, the number of1's included in this codeword, i.e., the Hamming distance is 3. Theleast value among the Hamming distance values of several codewords iscalled a “minimum distance (dmin)”. The linear error correcting code hassuperior error correcting performance (or capability), as the minimumdistance is increased more and more.

[0037] The extended Reed-Muller code can be derived from a sequencedetermined by the sum (or XOR) of a specific sequence and an m-sequence.In order to use a sequence family (or group) including the sum of thesequences as its elements, the sequence family must have a large minimumdistance. Such specific sequence family includes a Kasami sequencefamily, a Gold sequence family and a Kerdock code family. Such specificsequences have a minimum distance of (2^(2m)−2^(m))/2 for the fulllength L=2^(2m), and a minimum distance of 2^(2m)−2^(m) for the fulldistance L=2^(2m+1). That is, the minimum distance is 28 for the fulllength 64.

[0038] Now, a description will be made regarding a method for creatingan extended error correcting code which is a linear error correctingcode having high performance, using the above stated sequence families.

[0039] According to a coding theory, there exists a column permutationfunction for creating a Walsh code by cyclic-shifting the m-sequence.The m-sequence becomes a Walsh code when the sequences comprised of thespecific sequence and the m-sequence are subjected to column permutationusing the column permutation function. The minimum distance by the sum(XOR) of the specific sequence and the Walsh code satisfies the optimalcode property. Herein, a sequence obtained by column-permuting thespecific sequence will be referred to as a “mask function (or masksequence).” FIG. 5 illustrates a scheme for encoding the linear errorcorrecting code. As illustrated, the present invention provides a TFCIencoding scheme for making a complete coded symbol (or TFCI codeword) byadding a first coded symbol (or mask function) created by a first TFCIbit and a second coded symbol (or orthogonal code) created by a secondTFCI bit.

[0040] Referring to FIG. 5, TFCI bits to be transmitted are divided intoa first TFCI bit and a second TFCI bit and then, provided to a maskfunction generator 502 and a Walsh code generator 504, respectively. Themask function generator 504 outputs a given mask sequence by encodingthe first TFCI bit, and the Walsh code generator 504 outputs a givenorthogonal sequence by encoding the second TFCI bit. An adder 510 thenadds (XORs) the mask sequence from the mask function generator 502 andthe orthogonal sequence from the orthogonal code generator 504, andoutputs a complete TFCI codeword (or TFCI coded symbol). The maskfunction generator 502 may have mask sequences associated with every setof the first TFCI bits in the form of a coding table. The orthogonalcode generator 504 may also have orthogonal sequences associated withevery set of the second TFCI bits in the form of a coding table.

[0041] Now, a description will be made of a method for creating the maskfunctions (or mask sequences) in the case where a (2^(n), n+k) code iscreated using the Kasami sequence. Here, the “(2^(n), n+k) code” refersto a code for outputting a TFCI codeword (or coded symbol) comprised of2^(n) symbols by receiving (n+k) TFCI bits (input information bits).Actually, it is known that the Kasami sequence is represented by the sumof different m-sequences. Therefore, in order to create the (2^(n), n+k)code, a Kasami sequence of length 2^(n−1) must be created first. TheKasami sequence is equivalent to the sum of an m-sequence created by agenerator polynomial f1(x) and a sequence obtained by repeating2^((n/2))+1 times a sequence of length 2^((n/2))−1 determined bydecimating the m-sequence in a unit of 2^((n/2))+1. In addition, if thegenerator polynomial is determined, the respective m-sequences m(t),i.e., m₁(t) and m₂(t) can be calculated using a trace function inaccordance with Equation (1) below. $\begin{matrix}{{{m_{1}(t)} = {{Tr}\left( {A\quad \alpha^{t}} \right)}},{t = 0},1,\quad \ldots \quad,{30\quad {where}},{{{Tr}(\alpha)} = {\sum\limits_{k = 0}^{n - 1}\alpha^{2^{k}}}},{\alpha \in {{GF}\left( 2^{n} \right)}}} & {{Equation}\quad (1)}\end{matrix}$

[0042] In Equation (1), A indicates a value determined according to aninitial value of the m-sequence, a indicates a root of the generatorpolynomial, and n indicates the degree of the generator polynomial.

[0043]FIG. 6 illustrates a procedure for creating the mask function inthe case where the (2^(n), n+k) code (i.e., a code for outputting a2^(n)-bit coded symbol by receiving (n+k) input information bits) iscreated using the Kasami sequence among the above-mentioned sequences.It is known that the Kasami sequence is represented by the sum of thedifferent m-sequences. Therefore, in order to create the (2^(n), n+k)code, a Kasami sequence of length 2^(n)−1 must be created first. TheKasami sequence, as described above, is created by the sum of anm-sequence created by a generator polynomial f1(x) and a sequenceobtained by repeating 2^((n/2))+1 times a sequence of length 2^((n/2))−1determined by decimating the m-sequence in a unit of 2^((n/2))+1.

[0044] Referring to FIG. 6, in step 610, an m-sequence m₁(t) created bythe generator polynomial f1(x) and a sequence m₂(t) obtained byrepeating 2^((n/2))+1 times a sequence of length 2^((n/2))−1 determinedby decimating the m-sequence m₂(t) in a unit of 2^((n/2))+1 arecalculated in accordance with Equation (1). In step 620, a columnpermutation function σ(t) for converting the m-sequence m₁(t) into aWalsh code shown in Equation (2) below is calculated. $\begin{matrix}{{\sigma:\left. \left\{ {0,1,2,\quad \ldots \quad,{2^{n} - 2}} \right\}\rightarrow\left\{ {1,2,\quad \ldots \quad,{2^{n} - 1}} \right\} \right.}{{\sigma (t)} = {\sum\limits_{i = 0}^{n - 1}{{m_{1}(t)}2^{n - 1 - i}}}}} & {{Equation}\quad (2)}\end{matrix}$

[0045] In step 630, 7 sequence families obtained by cyclic-shifting them-sequence m₂(t) 0 to 6 times are subjected to column permutation usingσ⁻¹(t)+2, where σ⁻¹(t) is an inverse function of the column permutationfunction σ(t) for converting the sequence m₁(t) to the Walsh code.Further, ‘0’ is added to the head of every sequence created by thecolumn permutation so as to make the sequences have a length 2^(n),thereby creating 2^(n)−1 sequence families di(t) of length 2^(n), wherei=0, . . . , 2^(n)−1 and t=1, . . . , 2^(n). The sequence familiescreated in step 630 can be represented by Equation (3) below.$\begin{matrix}\left\{ {{\left. {{d_{i}(t)}{{{t = 1},\quad \ldots \quad,{2n},{i = 0},\quad \ldots \quad,{2^{\frac{n}{2}} - 2}}}} \right\} {d_{i}(t)}} = \begin{pmatrix}{0,} & {{{if}\quad t} = 1} \\{{m_{d}\left( {t + i - 2} \right)},} & {{{{if}\quad t} = 1},2,3,\quad \ldots \quad,2^{n}}\end{pmatrix}} \right. & {{Equation}\quad (3)}\end{matrix}$

[0046] The calculated sequence families di(t) are mask functions whichcan be used as 7 masks.

[0047] One of the properties of the calculated sequence families di(t)is that a mask created by adding two different masks out of the abovemasks becomes another mask out of the 2^((n/2))−1 masks. To generalizefurther, all of the 2^((n/2))−1 masks including a mask of all 0's can berepresented by a predefined sum of n masks out of the 2^((n/2))−1 masks.The n masks are defined as base sequences (or basis sequences).

[0048] The total number of codewords required in creating the (2^(n),n+k) code is 2^(n+k) which is the number of possible sets of the inputinformation bits. Here, the number of biorthogonal sequences indicating2^(n) orthogonal sequences (or Walsh sequences) and their complements is2^(n)×2=2^(n)−1, and the number of non-zero masks required to create the(2^(n), n+k) code is (2^(n+k)/2^(n+1))−1=2^(k−1)−1. In addition, all ofthe 2^(k−1)−1 masks can also be represented by a predefined sum of the(k−1) masks on the basis of the property similar to that describedabove.

[0049] Next, a method for selecting the (k−1) masks will be described.In step 630, a sequence family is created by cyclic-shifting the m₂(t) 0to 2^((n/2))−1 times. An m-sequence created by cyclic-shifting the m₂(t)i times can be expressed as Tr(α^(i)·α^(t)) using Equation (1). That is,a sequence family created by cyclic-shifting the m₂(t) 0 to 6 timesinclude the sequences created according to initial values A=1, α, . . ., α² ^(n) ⁻². At this moment, (k−1) linearly independent base elementsare searched from the Galois elements 1, α, . . . , α² ^(n) ⁻². Thesequences corresponding to the output sequences of the trace functiontaking the (k−1) base elements as initial values become base masksequences. In this process, the linearly independent condition isrepresented by Equation (4) below.

α₁, . . . , α_(k−1): linearly independent

c _(a)α₁ +c ₂α₂ + . . . +c _(k−1)α_(k−1)≠0, ∀c ₁ , c ₂ , . . . , c_(k−1)  Equation (4)

[0050] A method for creating the generalized mask function will bedescribed with reference to FIG. 6, for the case where a (64, 10) codeis created using the Kasami sequence family. Actually, it is well knownthat the Kasami sequence is represented by the sum of the differentm-sequences. Therefore, in order to create the (64, 10) code, a Kasamisequence of length 63 must be created first. The Kasami sequence iscomprised of an m-sequence created by a generator polynomial x⁶+x+1 anda sequence created by repeating 2^((n/2))+1 times a sequence of length2^((n/2))−1 determined by decimating the m-sequence in a unit of2^((n/2))+1. Here, if the generator polynomial is determined, eachm-sequence m(t) can be calculated using the trace function as shown inEquation (5) below. $\begin{matrix}{{{m_{1}(t)} = {{Tr}\left( {A\quad \alpha^{t}} \right)}},{t = 0},1,\quad \ldots \quad,{63\quad {where}},{{{Tr}(\alpha)} = {\sum\limits_{n = 0}^{4}\alpha^{2^{n}}}},{\alpha \in {{GF}\left( 2^{5} \right)}}} & {{Equation}\quad (5)}\end{matrix}$

[0051] In Equation (5), A indicates a value determined according to aninitial value of the m-sequence and cc indicates a root of the generatorpolynomial. In addition, n=6 because the generator polynomial is of the6^(th) degree.

[0052]FIG. 6 illustrates a procedure for creating the mask function inthe case where the (64, 10) code (i.e., a code for outputting a 64-bitcoded symbol by receiving 10 input information bits) is created using aKasami sequence family among the above-stated sequence families.Referring to FIG. 6, in step 610, an m-sequence m₁(t) created by thegenerator polynomial x⁶+x+1 and a sequence m₂(t) obtained by repeating2^((n/2))+1 times a sequence of length 2^((n/2))−1 determined bydecimating the m-sequence m₂(t) in a unit of 2^((n/2))+1 are calculatedin accordance with Equation (5). In step 620, a column permutationfunction σ(t) for converting the m-sequence m₁(t) into a Walsh codeshown in Equation (6) below is calculated. $\begin{matrix}{{\sigma:\left. \left\{ {0,1,2,\quad \ldots \quad,63} \right\}\rightarrow\left\{ {1,2,\quad \ldots \quad,64} \right\} \right.}{{\sigma (t)} = {\sum\limits_{i = 0}^{4}{{m_{1}(t)}2^{4 - i}}}}} & {{Equation}\quad (6)}\end{matrix}$

[0053] In step 630, 7 sequence families obtained by cyclic-shifting them-sequence m₂(t) 0 to 6 times are subjected to column permutation usingσ⁻¹(t)+2, where σ⁻¹(t) is an inverse function of the column permutationfunction σ(t) for converting the sequence m₁(t) to the Walsh code.Further, ‘0’ is added to the head of every sequence created by thecolumn permutation so as to make the sequences have a length 64, therebycreating 7 sequence families di(t) of length 64, where i=0, . . . , 6and t=1, . . . , 64. The sequence families created in step 630 can berepresented by Equation (7) below. $\begin{matrix}\left\{ {{{d_{i}(t)}\left. {{t = 1},\quad \ldots \quad,64,{i = 0},\quad \ldots \quad,6} \right\} {d_{i}(t)}} = \begin{pmatrix}{0,} & {{{if}\quad t} = 1} \\{{m_{d}\left( {t + i - 2} \right)},} & {{{{if}\quad t} = 1},2,3,\quad \ldots \quad,64}\end{pmatrix}} \right. & {{Equation}\quad (7)}\end{matrix}$

[0054] The sequence families di(t) calculated by Equation (7) are maskfunctions which can be used as 7 mask sequences.

[0055] One of the properties of the calculated sequence families di(t)is that a mask created by adding two different masks out of the abovemasks becomes another mask out of the 7 masks. To generalize further,all of the 7 masks can be represented by a predefined sum of 3 masks outof the 7 masks. As mentioned above, all of the mask sequences which canbe represented by the predefined sum of the masks, are defined as basesequences.

[0056] The total number of codewords required in creating the (64, 10)code is 2¹⁰=1024, which is the number of possible sets of the inputinformation bits. Here, the number of biorthogonal codewords of length64 is 64×2=128, and the number of masks required to create the (64, 10)code is (1024/128)−1=7. In addition, all of the 7 masks can also berepresented by a predefined sum of the 3 masks on the basis of theproperty similar to that described above. Therefore, a method forselecting the 3 masks is required. The method for selecting the 3 maskswill be described below. In step 630, a sequence family is created bycyclic-shifting the m₂(t) 0 to 6 times. An m-sequence created bycyclic-shifting the m₂(t) i times can be expressed as Tr(α^(i)·α^(t))using Equation (5). That is, a sequence family created bycyclic-shifting the m₂(t) 0 to 6 times include the sequences createdaccording to initial values A=1, α, . . . , α⁶. At this moment, 3linearly independent base elements are searched from the Galois elements1, α, . . . , α⁶. It is possible to create all the 7 masks by thepredefined sum of the 3 masks by selecting the sequences taking the 3base elements as initial values. In this process, the linearlyindependent condition is represented by Equation (8) below.

α, β, γ, δ: linearly independent

c ₁ α+c ₂ β+c ₃ γ+c ₄δ≠0, ∀c ₁ , c ₂ , c ₃ , c ₄  Equation (8)

[0057] Actually, 1, α and α² in the Galois field GF(2³) are basispolynomials well known as the above 4 linear independent elements.Therefore, the following 3 mask functions M1, M2 and M4 are calculatedby substituting the basis polynomials into Equation (5)

[0058]M1=0011010101101111101000110000011011110110010100111001111111000101

[0059]M2=0100011111010001111011010111101101111011000100101101000110111000

[0060]M3=0001100011100111110101001101010010111101101111010111000110001110

[0061] Now, a detailed description will be made regarding an apparatusand method for encoding and decoding a TFCI in a NB-TDD CDMA mobilecommunication system according to an embodiment of the presentinvention. In the embodiments of the present invention, the encoder andthe decoder use the base mask sequences calculated in the above method.Specifically, a method for creating the base mask sequences will bedescribed below.

[0062] First Embodiment

[0063]FIG. 7A illustrates an apparatus for encoding a TFCI in a NB-TDDCDMA mobile communication system according to a first embodiment of thepresent invention. Referring to FIG. 7A, 10 input information bits a0-a9are provided to their associated multipliers 740-749, respectively. Abase Walsh code generator 710 generates base Walsh codes having apredetermined length. Here, the “base Walsh codes” refer topredetermined Walsh codes, by a predetermined sum of which all ofdesired Walsh codes can be created. For example, for a Walsh code oflength 64, the base Walsh codes include a 1^(st) Walsh code W1, a 2^(nd)Walsh code W2, a 4^(th) Walsh code W4, an 8^(th) Walsh code W8, a16^(th) Walsh code W16 and a 32^(nd) Walsh code W32. A 1-bit generator700 continuously generates a predetermined code bit. That is, as theinvention is applied to the biorthogonal sequences, the 1-bit generator700 generates a bit required for using orthogonal sequences asbiorthogonal codes. For example, the 1-bit generator 700 constantlygenerates a bit having a value ‘1’, thereby to invert the Walsh codesgenerated from the base Walsh code generator 710.

[0064] The Walsh code generator 710 simultaneously outputs Walsh codesW1, W2, W4, W8, W16 and W32 of length 64. The multiplier 740 multipliesthe 1^(st) Walsh code W1(=0101010101010101010101010101010101010101010101010101010101010101) fromthe Walsh code generator 710 by the first input information bit a0. Themultiplier 741 multiplies the 2^(nd) Walsh code W2(=0011001100110011001100110011001100110011001100110011001100110011) fromthe Walsh code generator 710 by the second input information bit a1. Themultiplier 742 multiplies the 4^(th) Walsh code W4(=0000111100001111000011110000111100001111) from the Walsh codegenerator 710 by the third input information bit a2. The multiplier 743multiplies the 8^(th) Walsh code W8(=0000000011111111000000001111111100000000111111110000000011111111) fromthe Walsh code generator 710 by the fourth input information bit a3. Themultiplier 744 multiplies the 16^(th) Walsh code W16(=0000000000000000111111111111111100000000000000001111111111111111) fromthe Walsh code generator 710 by the fifth input information bit a4. Themultiplier 745 multiplies the 32^(nd) Walsh code W32(=00000000000000000000000000000000111111111111111111 11111111111111)from the Walsh code generator 710 by the sixth input information bit a5.That is, the multipliers 740-745 multiply the input base Walsh codes W1,W2, W4, W8, W16 and W32 by their associated input information bits a0-a5in a symbol unit. Meanwhile, the multiplier 746 multiplies the symbolsof all 1's output from the 1-bit generator 700 by the seventh inputinformation bit a6.

[0065] A mask generator 720 generates mask sequences having apredetermined length. The method for generating the mask sequences willnot be described, since it has already been described above. Forexample, when the (64, 10) code is generated using the Kasami sequence,the base mask sequences include a 1^(st) mask sequence M1, a ^(nd) masksequence M2 and a 4^(th) mask sequence M4. The mask generator 720simultaneously outputs the mask functions M1, M2 and M4 of length 64.The multiplier 747 multiplies the 1^(st) mask function M1(=0011010101101111101000110000011011110110010100111001111111000101) fromthe mask generator 720 by the eighth input information bit a7. Themultiplier 748 multiplies the 2^(nd) mask function M2(=0100011111010001111011010111101101111011000100101101000110111000) fromthe mask generator 720 by the ninth input information bit a8. Themultiplier 749 multiplies the 4^(th) mask function M4(0001100011100111110101001101010010111101101111010111000110001110) fromthe mask generator 720 by the tenth input information bit a9. Themultipliers 747-749 multiply the input base mask sequences M1, M2 and M4by the associated input information bits a7-a9 in a symbol unit.

[0066] An adder 760 adds (or XORs) the symbols output from themultipliers 740-749 in a symbol unit, and then, outputs 64 codedsymbols. A symbol puncturer 770 punctures the 64 symbols output from theadder 760 according to a predetermined rule and outputs 48 symbols. Thatis, the (48, 10) encoder punctures 16 symbols from the 64 symbolscreated by the (64, 10) code. The minimum distance of the (48, 10)encoder varies depending on the positions of the 16 punctured symbols.Combinations of the 16 punctured positions, providing superiorperformance, are shown below. When using the following combinations ofthe punctured positions, the (48, 10) encoder has the minimum distanceof 18 and provides superior weight distribution.

[0067] {0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}

[0068] {0, 4, 8, 13, 16, 21, 25, 28, 32, 37, 43, 44, 49, 52, 56, 62}

[0069] {0, 4, 8, 13, 16, 21, 25, 31, 32, 37, 43, 44, 49, 52, 56, 61}

[0070] {0, 4, 8, 13, 18, 21, 25, 30, 35, 36, 40, 46, 50, 53, 57, 62}

[0071] {0, 4, 8, 13, 18, 21, 25, 30, 35, 37, 40, 47, 50, 53, 57, 62}

[0072] {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 49, 55, 58, 61}

[0073] {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 56, 63}

[0074] {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 58, 61}

[0075] {0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}

[0076]FIG. 8 illustrates a control flow for encoding a TFCI in an NB-TDDCDMA mobile communication system according to the first embodiment ofthe present invention. Referring to FIG. 8, in step 800, a sequence of10 input information bits a0-a9 is input and then, parameters code[] andj are initialized to ‘0’. The parameter code[] indicates the 64 codedsymbols finally output from the encoder and the parameter j is used tocount the 64 symbols constituting one codeword.

[0077] Thereafter, it is determined in step 810 whether the firstinformation bit a0 is ‘1’. If the first information bit a0 is ‘1’, the1^(st) Walsh code W1(=0101010101010101010101010101010101010101010101010101010101010101) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the first information bit a0 is not ‘1’, the control flowskips to step 812. After step 810, it is determined in step 812 whetherthe second information bit a1 is ‘1’. If the second information bit a1is ‘1’, the 2^(nd) Walsh code W2(=0011001100110011001100110011001100110011001100110011001100110011) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the second information bit a1 is not ‘1’, the control flowskips to step 814. After step 812, it is determined in step 814 whetherthe third information bit a2 is ‘1’. If the third information bit a2 is‘1’, the 4^(th) Walsh code W4(=0000111100001111000011110000111100001111000011110000111100001111) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the third information bit a2 is not ‘1’, the control flowskips to step 816. After step 814, it is determined in step 816 whetherthe fourth information bit a3 is ‘1’. If the fourth information bit a3is ‘1’, the 8^(th) Walsh code W8(=0000000011111111000000001111111100000000111111110000000011111111) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the fourth information bit a3 is not ‘1’, the control flowskips to step 818. After step 816, it is determined in step 818 whetherthe fifth information bit a4 is ‘1’. If the fifth information bit a4 is‘1’, the 16^(th) Walsh code W16(=0000000000000000111111111111111100000000000000001111111111111111) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the fifth information bit a4 is not ‘1’, the control flowskips to step 820. After step 818, it is determined in step 820 whetherthe sixth information bit a5 is ‘1’. If the sixth information bit a5 is‘1’, the 32^(nd) Walsh code W32(=0000000000000000000000000000000011111111111111111111111111111111) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the sixth information bit a5 is not ‘1’, the control flowjumps to step 822.

[0078] After step 820, it is determined in step 822 whether the seventhinformation bit a6 is ‘1’. If the seventh information bit a6 is ‘1’, asequence of all 1's is XORed with the coded symbol sequence parametercode[] of length 64. Otherwise, if the seventh information bit a6 is not‘1’, the control flow jumps to step 824. That is, in step 822, the Walshcode created in the preceding steps is XORed by 1 thereby to create abiorthogonal code. More specifically, if the seventh information bit a6is ‘1’, the parameter j is initialized to ‘0’ and a j^(th) parametercode[j] is XORed with ‘1’. Further, it is determined whether theparameter j is 63, in order to determine whether the parameter j is thelast symbol of the codeword. If the parameter j is not 63, this processis repeated after increasing the parameter j by 1. In other words, instep 822, when the seventh information bit a6 is ‘1’, a length-64sequence of all 1's is XORed with a coded symbol sequence of length 64.Therefore, after repeating this process 64 times, the control flowproceeds to step 824 from the step for determining whether the parameterj is 63.

[0079] After step 822, it is determined in step 824 whether the eighthinformation bit a7 is ‘1’. If the eighth information bit a7 is ‘1’, thefirst mask function M1(=0011010101101111101000110000011011110110010100111001111111000101) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the eighth information bit a7 is not ‘1’, the control flowskips to step 826. After step 824, it is determined in step 826 whetherthe ninth information bit a8 is ‘1’. If the ninth information bit a8 is‘1’, the second mask function M2(=0100011111010001111011010111101101111011000100101101000110111000) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the ninth information bit a8 is not ‘1’, the control flowskips to step 828. After step 826, it is determined in step 828 whetherthe tenth information bit a9 is ‘1’. If the tenth information bit a9 is‘1’, the fourth mask function M4(=000110001110011111010100110101001011110110 1111010111000110001110) isXORed with the coded symbol sequence parameter code[] of length 64.Otherwise, if the tenth information bit a9 is not ‘1’, the control flowskips to step 830. In step 830, only the sequences corresponding toinformation bits 1's out of the 10 sequences W1, W2, W4, W8, W16, W32,1, M1, M2 and M4 of length 64 associated respectively with the 10 inputinformation bits a0-a9 are all XORed to output a value of the codedsymbol sequence parameter code[].

[0080] The (64, 10) encoder operating in the method of FIG. 8 creates 64Walsh codes of length 64, 64 inverted Walsh codes determined byinverting the 64 Walsh codes, and a total of 896 codes determined by thecombination of a total of 7 mask sequences calculated by the combinationof a total of 128 orthogonal codes and 3 mask functions. Therefore, thetotal number of codewords is 1024. In addition, a (64, 9) encodercreates 64 Walsh codes of length 64, Walsh codes calculated by addingall 1's to (or multiplying −1 by, in case of a real number) symbols ofevery Walsh code among the 1024 codewords, and codes determined bycombining a total of 4 mask functions calculated by the combination of atotal of 128 orthogonal codes and 2 mask functions among the 3 maskfunctions, and a (64, 8) encoder creates 64 Walsh codes of length 64,Walsh codes calculated by adding all 1's to (or multiplying −1 by, incase of a real number) symbols of every Walsh code among the 1024codewords, and codes determined by combining a total of 2 mask functionscalculated by the combination of a total of 128 biorthogonal codes and 1mask function among the 3 mask functions. The (64, 9) encoder and the(64, 8) encoder both have a minimum distance of 28. The (64, 9) encodercan be realized using only two of the 3 mask functions output from themask function generator 720 of FIG. 7A, while the (64, 8) encoder can berealized using only one of the 3 mask functions output from the maskfunction generator 720. As stated above, the encoder can adaptivelyperform encoding according to the number of input information bits, andcan also have superior performance by increasing the minimum distancedetermining the performance of the encoder, as high as possible.

[0081] The (64, 10) encoder uses, as codewords, 64 Walsh codes of length64, 64 inverted Walsh codes calculated by inverting the 64 Walsh codes,and 896 sequences calculated by combining a total of 128 biorthogonalcodes with 7 masks functions of length 64, the structure of which isillustrated in FIG. 11.

[0082]FIG. 9 illustrates an apparatus for decoding a TFCI according toan embodiment of the present invention. Referring to FIG. 9, the decoderinserts ‘0’ in the positions, punctured by the encoder, of a receivedsignal corresponding to the TFCI symbol of length of 48, having a valueof +1/−1, thereby to create a received signal r(t) of length 64. Thereceived signal r(t) is provided to 7 multipliers 901-907 and acorrelation calculator 920. The received signal r(t) is a signal encodedby a predetermined Walsh code and a predetermined mask sequence in theencoder of the transmitter. A mask generator 910 creates possible maskfunctions M1-M7 which can be created by 3 base masks, and provides thegenerated mask functions to multipliers 901-907, respectively. Themultiplier 901 multiplies the received signal r(t) by the mask functionM1 output from the mask generator 910, and provides its output to acorrelation calculator 921. The multiplier 902 multiplies the receivedsignal r(t) by the mask function M2 output from the mask generator 910,and provides its output to a correlation calculator 922. The multiplier907 multiplies the received signal r(t) by the mask function M7 outputfrom the mask generator 910, and provides its output to a correlationcalculator 927. That is, the multipliers 901-907 multiply the receivedsignal r(t) by their associated mask functions M1-M7 from the maskgenerator 910, and provide their outputs to the associated correlationcalculators 921-927, respectively. By doing so, the received signal r(t)and the signals calculated by multiplying the received signal r(t) bythe possible 7 mask functions, i.e., a total of 8 signals are providedto the 8 correlation calculators 920-907, respectively. If thetransmitter has encoded the TFCI using a predetermined mask function,any one of the outputs from the multipliers 901-907 will be a maskfunction-removed signal. Then, the correlation calculators 920-927calculate 128 correlation values by correlating the received signal r(t)and the outputs of the multipliers 901-907 with 64 Walsh codes of length64 and 64 inverted Walsh codes calculated by inverting the 64 Walshcodes, i.e., a total of 128 bi-Walsh (or biorthogonal) codes. Thelargest one of the calculated correlation values, an index ofthen-correlated Walsh code and an index of the correlation calculatorare provided to a correlation comparator 940. The 128 Walsh codes havealready been defined above. The correlation calculator 920 calculates128 correlation values by correlating the received signal r(t) with 128bi-Walsh codes of length 64. Further, the correlation calculator 920provides the correlation comparator 940 with the largest one of thecalculated correlation values, an index of then-calculated Walsh codeand an index ‘0’ of the correlation calculator 920. Here, the index ofthe correlation calculator is equivalent to an index of the maskfunction indicating which mask function is multiplied by the receivedsignal for the signal input to the correlation calculator. However, themask index ‘0’ means that no mask is multiplied by the received signal.Further, the correlation calculator 921 also calculates 128 correlationvalues by correlating the received signal r(t) multiplied by the maskfunction M1 by the multiplier 901 with 128 bi-Walsh codes of length 64.Further, the correlation calculator 921 provides the correlationcomparator 940 with the largest one of the calculated correlationvalues, an index of then-calculated Walsh code and an index ‘1’ of thecorrelation calculator 921. The correlation calculator 922 calculates128 correlation values by correlating the received signal r(t)multiplied by the mask function M2 by the multiplier 902 with 128bi-Walsh codes of length 64. Further, the correlation calculator 922provides the correlation comparator 940 with the largest one of the 128calculated correlation values, an index of then-calculated Walsh codeand an index ‘2’ of the correlation calculator 922. The correlationcalculator 927 calculates 128 correlation values by correlating thereceived signal r(t) multiplied by the mask function M7 by themultiplier 907 with 128 bi-Walsh codes of length 64. Further, thecorrelation calculator 927 provides the correlation comparator 940 withthe largest one of the calculated correlation values, an index ofthen-calculated Walsh code and an index ‘7’ of the correlationcalculator 927.

[0083] The correlation comparator 940 then compares the 8 largestcorrelation values provided from the correlation calculators 920-927,and determines the largest one of them. After determining the largestcorrelation value, the correlation comparator 940 outputs TFCIinformation bits transmitted from the transmitter according to the indexof the Walsh code provided from the correlation calculator associatedwith the determined correlation value and an index (or mask index) ofthe same correlation calculator. That is, the correlation comparator 940determines a decoded signal of the received signal using the index ofthe Walsh code and the index of the mask function.

[0084]FIG. 10 illustrates a procedure for determining a Walsh code indexand a mask function index for the largest correlation value by comparingthe 8 correlation values in the correlation comparator 940 according tothe first embodiment of the present invention, and outputting the TFCIinformation bits accordingly. Referring to FIG. 10, in step 1000, afrequency indicating index parameter i is initialized to 1, and amaximum value, a Walsh code index and a mask index are all initializedto ‘0’. In step 1010, the correlation value, the Walsh code index forthe correlation value and the mask index, output from the firstcorrelation calculator 920, are stored as a first maximum value, a firstWalsh code index and a first mask sequence index, respectively.Thereafter, in step 1020, the first maximum value is compared with apreviously stored maximum value. If the first maximum value is largerthan the previously stored maximum value, the procedure goes to step1030. Otherwise, if the first maximum value is smaller than or equal tothe previously stored maximum value, the procedure proceeds to step1040. In step 1030, the first maximum value is designated as the maximumvalue, and the first Walsh code index and the first mask index aredesignated as the Walsh code index and the mask index, respectively. Instep 1040, a value set for the index parameter i is compared with thenumber ‘8’ of the correlation calculators, in order to determine whethercomparison has been completely performed on all of the 8 correlationvalues. If the frequency indicating index i is not equal to the number‘8’ of the correlation calculators in step 1040, the correlationcomparator 940 increases the frequency indicating index i by 1 in step1060 and thereafter, returns to step 1010 to repeat the above-describedprocess using the i^(th) maximum value, the i^(th) Walsh code index andthe i^(th) mask index, output from the increased i^(th) correlationcalculator. After the above process is repeatedly performed on the8^(th) maximum value, the 8^(th) Walsh code index and the 8^(th) maskindex, the frequency indicating index i becomes 8. Then, the proceduregoes to step 1050. In step 1050, the correlation comparator 940 outputsdecoded bits (TFCI information bits) associated with the Walsh codeindex and the mask index. The Walsh code index and the mask indexcorresponding to the decoded bits are the Walsh code index and the maskindex corresponding to the largest one of the 8 correlation valuesprovided from the 8 correlation calculators.

[0085] In the first embodiment, the (48, 10) encoder creates 48 symbolsby puncturing 16 symbols after creating 64 codes. In the secondembodiment below, however, unlike FIG. 7A, the encoder outputs 48symbols after puncturing 16 symbols according to a predeterminedpuncturing pattern in the Walsh code generator, the 1-bit generator andthe mask generator.

[0086] Second Embodiment

[0087] The encoding apparatus according to the second embodiment of thepresent invention is similar in structure to the encoder described withreference to the first embodiment. However, the only difference is thatthe sequences output from the 1-bit generator, the Walsh code generatorand the mask generator are the sequences of length 48, to which apuncturing pattern is previously applied. For example, the sequencesoutput from the Walsh code generator, the 1-bit generator and the maskgenerator according to the first embodiment, from which 0^(th), 4^(th),8^(th), 13^(th), 16^(th), 20^(th), 27^(th), 31^(st), 34^(th), 38^(th),41^(st), 44^(th), 50^(th), 54^(th), 57^(th) and 61^(st) terms arepunctured, are used in the second embodiment.

[0088]FIG. 7B illustrates an apparatus for encoding a TFCI in an NB-TDDCDMA mobile communication system according to the second embodiment ofthe present invention. Referring to FIG. 7B, 10 input information bitsa0-a9 are provided to their associated multipliers 7400, 7410, 7420,7430, 7440, 7450, 7460, 7470, 7480 and 7490, respectively. A base Walshcode generator 7100 simultaneously generates Walsh codes W1′, W2′, W4′,W8′, W16′ and W32′ of length 48, calculated by puncturing the base Walshcodes according to a predetermined puncturing rule as described above.Here, the “base Walsh codes” refer to predetermined Walsh codes, by apredetermined sum of which all of desired Walsh codes can be created.For example, for a Walsh code of length 64, the base Walsh codes includea 1^(st) Walsh code W1, a 2^(nd) Walsh code W2, a 4^(th) Walsh code W4,an 8^(th) Walsh code W8, a 16^(th) Walsh code W16 and a 32^(nd) Walshcode W32. A 1-bit generator 7000 continuously generates a predeterminedcode bit. The multiplier 7400 multiplies the Walsh code W1′(=101101101001101101010010011011001101011011001001) punctured accordingto a predetermined puncturing rule by the Walsh code generator 7100 bythe input information bit a0. The multiplier 7410 multiplies thepunctured Walsh code W2′(=011011011011011011001001001001011011001001011011) from the Walsh codegenerator 7100 by the input information bit a1. The multiplier 7420multiplies the punctured Walsh code W4′(=000111000111000111000111000111000111000111000111) from the Walsh codegenerator 7100 by the input information bit a2. The multiplier 7430multiplies the punctured Walsh code W8′(=000000111111000000111111000000111111000000111111) from the Walsh codegenerator 7100 by the input information bit a3. The multiplier 7440multiplies the punctured Walsh code W16′(=000000000000111111111111000000000000111111111111) from the Walsh codegenerator 7100 by the input information bit a4. The multiplier 7450multiplies the punctured Walsh code W32′(=000000000000000000000000111111111111111111111111) from the Walsh codegenerator 7100 by the input information bit multiplier 7460 multipliesthe symbols of all 1's output from the 1-bit generator 7000 by the inputinformation bit a6.

[0089] A mask generator 7200 simultaneously outputs punctured base maskfunctions M1′, M2′ and M4′ of length 48, determined by puncturing thebase masks according to a predetermined puncturing pattern. The methodfor creating the mask functions will not be described, since it hasalready been described above. The multiplier 7470 multiplies thepunctured mask function M1′(=011101110111010011000011111010001011101111100001) from the maskgenerator 7200 by the input information bit a7. The multiplier 7480multiplies the punctured mask function M2′(=100111101001110101011101011101001010111001111100) from the maskgenerator 7200 by the input information bit a8. The multiplier 7490multiplies the punctured mask function M4′(=001000110011101100110010101111111101011001100110) from the maskgenerator 7200 by the input information bit a9. That is, the multipliers7470-7490 multiply the input base mask sequences M1′, M2′ and M4′ by theassociated input information bits a7-a9 in a symbol unit. An adder 7600then adds (or XORs) the symbols output from the multipliers 7400-7490 ina symbol unit, and outputs 48 coded symbols (TFCI symbols).

[0090]FIG. 12 illustrates a control flow for encoding a TFCI in anNB-TDD CDMA mobile communication system according to the secondembodiment of the present invention. Referring to FIG. 12, in step 1200,a sequence of 10 input information bits a0-a9 is input and then,parameters code[] and j are initialized to ‘0’. Here, the coded symbolsequence parameter code[] indicates the 48 coded symbols finally outputfrom the encoder and the parameter j is used to count the 48 codedsymbols constituting one codeword.

[0091] Thereafter, it is determined in step 1210 whether the firstinformation bit a0 is ‘1’. If the first information bit a0 is ‘1’, thepunctured base Walsh code W1′(=101101101001101101010010011011001101011011001001) is XORed with thecoded symbol sequence parameter code[]. Otherwise, if the firstinformation bit a0 is not ‘1’, the control flow skips to step 1212.Specifically, if the information bit a0 is ‘1’, the parameter j isinitialized to ‘0’ and a j^(th) symbol of the first punctured Walsh codeW1′ is XORed with a j^(th) position code[] of the coded symbol sequenceparameter. Here, since j=0, the 0^(th) symbol of the first Walsh code isXORed with the 0^(th) position of the coded symbol sequence parameter.Further, it is determined whether the parameter j is 47, in order todetermine whether the parameter j indicates the last coded symbol. Ifthe parameter j is not equal to 47, the parameter j is increased by 1and then the above process is repeated. Otherwise, if the parameter j isequal to 47, the control flow proceeds to step 1212. That is, aftercompletion of XORing on the 48 coded symbols, the control flow proceedsto the next step.

[0092] After step 1210, it is determined in step 1212 whether the secondinformation bit a1 is ‘1’. If the second information bit a1 is ‘1’, thepunctured base Walsh code W2′(=011011011011011011001001001001011011001001011011) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if thesecond information bit a1 is not ‘1’, the control flow skips to step1214. After step 1212, it is determined in step 1214 whether the thirdinformation bit a2 is ‘1’. If the third information bit a2 is ‘1’, thepunctured base Walsh code W4′(000111000111000111000111000111000111000111000111) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if thethird information bit a2 is not ‘1’, the control flow skips to step1216. After step 1214, it is determined in step 1216 whether the fourthinformation bit a3 is ‘1’. If the fourth information bit a3 is ‘1’, thepunctured base Walsh code W8′(=000000111111000000111111000000111111000000111111) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if thefourth information bit a3 is not ‘1’, the control flow skips to step1218. After step 1216, it is determined in step 1218 whether the fifthinformation bit a4 is ‘1’. If the fifth information, bit a4 is ‘1’, thepunctured base Walsh code W16′(=000000000000111111111111000000000000111111111111) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if thefifth information bit a4 is not ‘1’, the control flow skips to step1220. After step 1218, it is determined in step 1220 whether the sixthinformation bit a5 is ‘1’. If the sixth information bit a5 is ‘1’, thepunctured base Walsh code W32′(=000000000000000000000000111111111111111111111111) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if thesixth information bit a5 is not ‘1’, the control flow jumps to step1222.

[0093] After step 1220, it is determined in step 1222 whether theseventh information bit a6 is ‘1’. If the seventh information bit a6 is‘1’, a length-48 sequence of all 1's is XORed with the coded symbolsequence parameter code[]. Otherwise, if the seventh information bit a6is not ‘1’, the control flow jumps to step 1224. That is, in step 1222,the symbols of the Walsh code created in the preceding steps areinverted to create a bi-Walsh code corresponding to the Walsh code,thereby to create 128 bi-Walsh codes of length 48.

[0094] After step 1222, it is determined in step 1224 whether the eighthinformation bit a7 is ‘1’. If the eighth information bit a7 is ‘1’, thebase mask function M1′(=011101110111010011000011111010001011101111100001) punctured accordingto a predetermined puncturing rule is XORed with the coded symbolsequence parameter code[] of length 48. Otherwise, if the eighthinformation bit a7 is not ‘1’, the control flow skips to step 1226.After step 1224, it is determined in step 1226 whether the ninthinformation bit a8 is ‘1’. If the ninth information bit a8 is ‘1’, thepunctured base mask function M2′(=100111101001110101011101011101001010111001111100) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if theninth information bit a8 is not ‘1’, the control flow skips to step1228. After step 1226, it is determined in step 1228 whether the tenthinformation bit a9 is ‘1’. If the tenth information bit a9 is ‘1’, thepunctured base mask function M4′(=0010001100111011000110010101111111101011001100110) is XORed with thecoded symbol sequence parameter code[] of length 48. Otherwise, if thetenth information bit a9 is not ‘1’, the control flow is ended. Afterthe process of FIG. 12, the coded symbols determined by XORing only thesequences corresponding to information bits 1's out of the 10 sequencesW1′, W2′, W4′, W8′, W16′, W32′, 1, M1′, M2′ and M4′ of length 32associated respectively with the 10 input information bits a0-a9 arestored in the parameter code[].

[0095] The (48, 10) encoder creates 1024 codewords by puncturing, forexample, 0^(th), 4^(th), 8^(th), 13^(th), 16^(th), 20^(th), 27^(th),31^(st), 34^(th), 38^(th), 41^(st), 44^(th), 50^(th), 54^(th), 57^(th)and 61^(st) symbols from all of the codewords (Walsh codes or maskfunctions) of length 64 described in the first embodiment. Therefore,the total number of the codewords is 1024. In addition, a (48, 9)encoder creates 64 Walsh codes of length 64 determined by puncturing0^(th), 4^(th), 8^(th), 13^(th), 16^(th), 20^(th), 27^(th), 31^(st),34^(th), 38^(th), 41^(st), 44^(th), 50^(th), 54^(th), 57^(th) and61^(st) symbols from the 64 Walsh codes of length 64, codes calculatedby adding all 1's to (or multiplying −1 by, in case of a real number)symbols of all the punctured Walsh codes among the 1024 codewords, andcodes determined by combining a total of 4 mask functions calculated bythe combination of a total of 128 codes and 2 mask functions among the 3punctured mask functions, and a (48, 8) encoder creates 64 Walsh codesof length 48, codes calculated by adding all 1's to (or multiplying −1by, in case of a real number) symbols of every punctured Walsh codeamong the 1024 codewords, and codes determined by combining a total of 2mask functions calculated by the combination of a total of 128 codes and1 mask function among the 3 punctured mask functions. The (48, 9)encoder and the (48, 8) encoder both have a minimum distance of 18.

[0096] The (48, 9) encoder can be realized using only two of the 3 maskfunctions output from the mask function generator of FIG. 7B, while the(48, 8) encoder can be realized using only one of the 3 mask functionsoutput from the mask function generator of FIG. 7B. In addition, a (48,7) encoder can be realized using none of the 3 mask functions outputfrom the mask function generator of FIG. 7B. As stated above, theencoder can adaptively perform encoding according to the number of inputinformation bits, and can also have superior performance by increasingthe minimum distance determining the performance of the encoder, as highas possible.

[0097] Next, a description of a decoder according to the secondembodiment of the present invention will be made with reference to FIG.9.

[0098] Referring to FIG. 9, a received signal r(t) corresponding to aTFCI symbol of length 48 having a value of +1/−1 is commonly input to 7multipliers 901-907. The received signal r(t) is a signal encoded by agiven punctured Walsh code and a given punctured mask sequence in theencoder (FIG. 7B) of the transmitter. A mask generator 910 creates everypossible mask function which can be created by the 3 base masks, i.e.,mask functions M1′-M7′ of length 48 punctured according to a givenpuncturing rule, and provides the generated mask functions tomultipliers 901-907, respectively. The multiplier 901 multiplies thereceived signal r(t) of length 48 by the mask function M1′ output fromthe mask generator 910, and provides its output to a correlationcalculator 921. The multiplier 902 multiplies the received signal r(t)by the mask function M2′ output from the mask generator 910, andprovides its output to a correlation calculator 922. The multiplier 907multiplies the received signal r(t) by the mask function M7′ output fromthe mask generator 910, and provides its output to a correlationcalculator 927. That is, the multipliers 901-907 multiply the receivedsignal r(t) by their associated mask functions M1′-M7′ from the maskgenerator 910, and provide their outputs to the associated correlationcalculators 921-927, respectively. By doing so, the received signal r(t)and the signals calculated by multiplying the received signal r(t) bythe possible 7 mask functions, i.e., a total of 8 signals, are providedto the 8 correlation calculators 920-907, respectively. If thetransmitter has encoded the TFCI bits using a predetermined maskfunction, any one of the outputs from the multipliers 901-907 will be amask function-removed signal. Then, the correlation calculators 920-927calculate 128 correlation values by correlating the received signal r(t)and the outputs of the multipliers 901-907 with 128 bi-Walsh codes oflength 48. The largest one of the calculated correlation values, anindex of then-correlated Walsh code and an index of the correlationcalculator are provided to a correlation comparator 940. Here, the indexof the correlation calculator is equivalent to an index of the maskfunction indicating which mask function is multiplied by the receivedsignal, for the signal input to the correlation calculator. However, themask index ‘0’ means that no mask is multiplied by the received signal.The correlation calculator 920 calculates correlation values bycorrelating the received signal r(t) with 128 biorthogonal codes oflength 48. Further, the correlation calculator 920 provides thecorrelation comparator 940 with the largest one of the calculatedcorrelation values, an index of then correlated Walsh code and an index‘0’ of the correlation calculator 920. At the same time, the correlationcalculator 921 also calculates 128 correlation values by correlating thereceived signal r(t) multiplied by the mask function M1′ by themultiplier 901 with 128 bi-Walsh codes of length 48. Further, thecorrelation calculator 921 provides the correlation comparator 940 withthe largest one of the calculated correlation values, an index ofthen-calculated Walsh code and an index ‘1’ of the correlationcalculator 921. The correlation calculator 922 calculates 128correlation values by correlating the received signal r(t) multiplied bythe mask function M2′ by the multiplier 902 with 128 bi-Walsh codes oflength 48. Further, the correlation calculator 922 provides thecorrelation comparator 940 with the largest one of the 128 calculatedcorrelation values, an index of then-calculated Walsh code and an index‘2’ of the correlation calculator 922. The correlation calculator 927calculates 128 correlation values by correlating the received signalr(t) multiplied by the mask function M7′ by the multiplier 907 with 128bi-Walsh codes of length 48. Further, the correlation calculator 927provides the correlation comparator 940 with the largest one of thecalculated correlation values, an index of then-calculated Walsh codeand an index ‘7’ of the correlation calculator 927.

[0099] The correlation comparator 940 then compares the 8 largestcorrelation values provided from the correlation calculators 920-927,and determines the largest one of them. After determining the largestcorrelation value, the correlation comparator 940 outputs TFCIinformation bits transmitted from the transmitter according to the indexof the Walsh code provided from the correlation calculator associatedwith the determined correlation value and an index (or an index of amask function multiplied by the received signal r(t)) of the samecorrelation calculator.

[0100] The correlation comparator according to the second embodiment hasthe same operation as that of the correlation comparator according tothe first embodiment. An operation of the correlation comparatoraccording to the second embodiment will be described below withreference to FIG. 10.

[0101] Referring to FIG. 10, in step 1000, a frequency indicating indexi is initialized to 1, and a maximum value, a Walsh code index and amask index are all initialized to ‘0’. In step 1010, the correlationvalue, the Walsh code index for the correlation value and the maskindex, output from the first correlation calculator 920, are stored as afirst maximum value, a first Walsh code index and a first mask sequenceindex, respectively. Thereafter, in step 1020, the first maximum valueis compared with a previously stored maximum value. If the first maximumvalue is larger than the previously stored maximum value, the proceduregoes to step 1030. Otherwise, if the first maximum value is smaller thanor equal to the previously stored maximum value, the procedure proceedsto step 1040. In step 1030, the first maximum value is designated as themaximum value, and the first Walsh code index and the first mask indexare designated as the Walsh code Index and the mask index, respectively.In step 1040, a count value set for the index parameter i is comparedwith the number ‘8’ of the correlation calculators, in order todetermine whether comparison has been completely performed on all of the8 correlation values. If the frequency indicating index i is not equalto the number ‘8’ of the correlation calculators in step 1040, thecorrelation comparator 940 increases the frequency indicating index i by1 in step 1060 and thereafter, returns to step 1010 to repeat theabove-described process using the i^(th) maximum value, the i^(th) Walshcode index and the i^(th) mask index, output from the increased i^(th)correlation calculator. After the above process is repeatedly performedon the 8^(th) maximum value, the 8^(th) Walsh code index and the 8^(th)mask index, the frequency indicating index i becomes 8. Then, theprocedure goes to step 1050. In step 1050, the correlation comparator940 outputs decoded bits (TFCI bits) associated with the Walsh codeindex and the mask index. The Walsh code index and the mask indexcorresponding to the decoded bits are the Walsh code index and the maskindex corresponding to the largest one of the 8 correlation valuesprovided from the 8 correlation calculators.

[0102] As described above, the novel NB-TDD CDMA mobile communicationsystem according to the present invention can efficiently encode anddecode the TFCI, so as to increase error correcting capability.

[0103] While the invention has been shown and described with referenceto a certain preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. An apparatus for encoding k consecutive inputbits indicating a TFCI (Transport Format Combination Indicator) of eachof successively transmitted frames into a sequence of m symbols in anNB-TDD (Narrowband-Time Division Duplex) mobile communication system,comprising: an encoder for encoding the k input bits into a sequence ofat least 2^(n) symbols where 2^(n)>m, using an extended Reed-Muller codefrom a Kasami sequence; and a puncturer for performing puncturing on thesequence of 2^(n) symbols from the encoder so as to output a sequence ofm symbols.
 2. The apparatus as claimed in claim 1, wherein the encodercomprises: a 1-bit generator for generating a sequence of same symbols;a base orthogonal sequence generator for generating a plurality of baseorthogonal sequences; a base mask sequence generator for generating aplurality of base mask sequences; and an operator for receiving the TFCIincluding a first information part indicating conversion to abiorthogonal sequence, a second information part indicating conversionto an orthogonal sequence and a third information part indicatingconversion to a mask sequence, and generating the sequence of 2^(n)symbols by combining an orthogonal sequence selected from the baseorthogonal sequences by the second information part, a biorthogonalsequence constructed by a combination of the selected orthogonalsequence and the same symbols selected by the first information part,and a mask sequence selected by the third information part.
 3. Theapparatus as claimed in claim 1, wherein the encoder creates a (64, 10)code.
 4. The apparatus as claimed in claim 2, wherein the baseorthogonal sequences include a 1^(st) Walsh code, a 2^(nd) Walsh code, a4^(th) Walsh code, an 8^(th) Walsh code, a 16^(th) Walsh code and a32^(nd) Walsh code, selected from 64 orthogonal sequences of length 64.5. The apparatus as claimed in claim 2, wherein the base mask sequencesinclude a 1^(st) mask sequence of0011010101101111101000110000011011110110010100111001111111000101, a2^(nd) mask sequence of0100011111010001111011010111101101111011000100101101000110111000, and a4^(th) mask sequence of0001100011100111110101001101010010111101101111010111000110001110.
 6. Theapparatus as claimed in claim 2, wherein the operator comprises: a firstmultiplier for multiplying the same symbols by the first informationpart; a plurality of second multipliers for multiplying the baseorthogonal sequences by TFCI bits constituting the second informationpart; a plurality of third multipliers for multiplying the base masksequences by TFCI bits constituting the third information part; and anadder for generating the sequence of 2^(n) symbols by adding outputs ofthe first to third multipliers.
 7. The apparatus as claimed in claim 2,wherein the puncturer performs puncturing according to any one ofpuncturing patterns given below: {0, 4, 8, 13, 16, 20, 27, 31, 34, 38,41, 44, 50, 54, 57, 61} {0, 4, 8, 13, 16, 21, 25, 28, 32, 37, 43, 44,49, 52, 56, 62} {0, 4, 8, 13, 16, 21, 25, 31, 32, 37, 43, 44, 49, 52,56, 61} {0, 4, 8, 13, 18, 21, 25, 30, 35, 36, 40, 46, 50, 53, 57, 62}{0, 4, 8, 13, 18, 21, 25, 30, 35, 37, 40, 47, 50, 53, 57, 62} {0, 4, 8,13, 19, 22, 27, 30, 33, 36, 41, 44, 49, 55, 58, 61} {0, 4, 8, 13, 19,22, 27, 30, 33, 36, 41, 44, 50, 52, 56, 63} {0, 4, 8, 13, 19, 22, 27,30, 33, 36, 41, 44, 50, 52, 58, 61} {0, 4, 8, 13, 16, 20, 27, 31, 34,38, 41, 44, 50, 54, 57, 61}
 8. An apparatus for encoding k consecutiveinput bits indicating a TFCI of each of successively transmitted framesinto a sequence of m symbols in an NB-TDD mobile communication system,comprising: an orthogonal sequence generator for creating a plurality ofbiorthogonal sequences having a length of at least 2^(n) where 2^(n)>m,and outputting a biorthogonal sequence selected from the biorthogonalsequences by first information bits of the TFCI; a mask sequencegenerator for creating a plurality of mask sequences, whose minimumdistance by a sum of the mask sequences and the biorthogonal sequencesis at least 20, using a Kasami sequence, and outputting a mask sequenceselected from the mask sequences by second information bits of the TFCI;an adder for adding a biorthogonal sequence from the orthogonal sequencegenerator and a mask sequence from the mask sequence generator; and apuncturer for performing puncturing on the sequence of 2^(n) symbolsfrom the adder so as to output the sequence of m symbols.
 9. Theapparatus as claimed in claim 8, wherein the puncturer performspuncturing according to one of following puncturing patterns: {0, 4, 8,13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61} {0, 4, 8, 13, 16,21, 25, 28, 32, 37, 43, 44, 49, 52, 56, 62} {0, 4, 8, 13, 16, 21, 25,31, 32, 37, 43, 44, 49, 52, 56, 61} {0, 4, 8, 13, 18, 21, 25, 30, 35,36, 40, 46, 50, 53, 57, 62} {0, 4, 8, 13, 18, 21, 25, 30, 35, 37, 40,47, 50, 53, 57, 62} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 49,55, 58, 61} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 56,63} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 58, 61} {0, 4,8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}
 10. An apparatusfor encoding k consecutive input bits indicating a TFCI of each ofsuccessively transmitted frames into a sequence of m symbols in anNB-TDD mobile communication system, comprising: a 1-bit generator forcontinuously generating same symbols; an orthogonal sequence generatorfor creating first sequences having a length m by puncturing a pluralityof base orthogonal sequences having a length of at least 2^(n) where2^(n)>m, according to a predetermined puncturing pattern; a masksequence generator for creating second sequences having a length m bypuncturing base mask sequences having a length of at least 2^(n) where2^(n)>m; a plurality of multipliers provided in association with inputTFCI bits, for multiplying the same symbols, the first sequences and thesecond sequences by associated TFCI bits; and an adder for adding outputsequences of the multipliers and outputting a symbol sequence indicatingthe TFCI.
 11. The apparatus as claimed in claim 10, wherein the baseorthogonal sequences include a 1^(st) Walsh code, a 2^(nd) Walsh code, a4^(th) Walsh code, an 8^(th) Walsh code, a 16^(th) Walsh code and a32^(nd) Walsh code, selected from orthogonal sequences of length
 64. 12.The apparatus as claimed in claim 10, wherein the base mask sequencesinclude a 1^(st) mask sequence of0011010101101111101000110000011011110110010100111001111111000101, a2^(nd) mask sequence of0100011111010001111011010111101101111011000100101101000110111000, and a4^(th) mask sequence of0001100011100111110101001101010010111101101111010111000110001110. 13.The apparatus as claimed in claim 10, wherein the predeterminedpuncturing pattern is one of following puncturing patterns: {0, 4, 8,13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61} {0, 4, 8, 13, 16,21, 25, 28, 32, 37, 43, 44, 49, 52, 56, 62} {0, 4, 8, 13, 16, 21, 25,31, 32, 37, 43, 44, 49, 52, 56, 61} {0, 4, 8, 13, 18, 21, 25, 30, 35,36, 40, 46, 50, 53, 57, 62} {0, 4, 8, 13, 18, 21, 25, 30, 35, 37, 40,47, 50, 53, 57, 62} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 49,55, 58, 61} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 56,63} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 58, 61} {0, 4,8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}
 14. A method forencoding k consecutive input bits indicating a TFCI of each ofsuccessively transmitted frames into a sequence of m symbols in anNB-TDD mobile communication system, comprising: encoding the k inputbits into a sequence of at least 2^(n) symbols where 2^(n)>m, using anextended Reed-Muller code from a Kasami sequence; and performingpuncturing on the sequence of 2^(n) symbols so as to output a sequenceof m symbols.
 15. The method as claimed in claim 14, wherein theencoding step comprises the steps of: generating a sequence of samesymbols; generating a plurality of base orthogonal sequences; generatinga plurality of base mask sequences; and receiving the TFCI including afirst information part indicating conversion to a biorthogonal sequence,a second information part indicating conversion to an orthogonalsequence and a third information part indicating conversion to a masksequence, and generating the sequence of 2^(n) symbols by combining anorthogonal sequence selected from the base orthogonal sequences by thesecond information part, a biorthogonal sequence constructed by acombination of the selected orthogonal sequence and the same symbolsselected by the first information part, and a mask sequence selected bythe third information part.
 16. The method as claimed in claim 15,wherein the base orthogonal sequences include a 1^(st) Walsh code, a2^(nd) Walsh code, a 4^(th) Walsh code, an 8^(th) Walsh code, a 16^(th)Walsh code and a 32^(nd) Walsh code, selected from 64 orthogonalsequences of length
 64. 17. The method as claimed in claim 15, whereinthe base mask sequences include a 1^(st) mask sequence of0011010101101111101000110000011011110110010100111001111111000101, a2^(nd) mask sequence of0100011111010001111011010111101101111011000100101101000110110111000, anda 4^(th) mask sequence of0001100011100111110101001101010010111101101111010111000110001110. 18.The method as claimed in claim 14, wherein the puncturing is performedaccording to any one of puncturing patterns given below: {0, 4, 8, 13,16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61} {0, 4, 8, 13, 16, 21,25, 28, 32, 37, 43, 44, 49, 52, 56, 62} {0, 4, 8, 13, 16, 21, 25, 31,32, 37, 43, 44, 49, 52, 56, 61} {0, 4, 8, 13, 18, 21, 25, 30, 35, 36,40, 46, 50, 53, 57, 62} {0, 4, 8, 13, 18, 21, 25, 30, 35, 37, 40, 47,50, 53, 57, 62} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 49, 55,58, 61} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 56, 63}{0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 58, 61} {0, 4, 8,13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}
 19. A method forencoding k consecutive input bits indicating a TFCI of each ofsuccessively transmitted frames into a sequence of m symbols in anNB-TDD mobile communication system, comprising: creating a plurality ofbiorthogonal sequences having a length of at least 2^(n) where 2^(n)>m,and outputting a biorthogonal sequence selected from the biorthogonalsequences by first information bits of the TFCI; creating a plurality ofmask sequences, whose minimum distance by a sum of the mask sequencesand the biorthogonal sequences is at least 20, using a Kasami sequencerepresented by a sum of two m-sequences, and outputting a mask sequenceselected from the mask sequences by second information bits of the TFCI;adding the selected biorthogonal sequence and the mask sequence; andperforming puncturing on the sequence of 2^(n) symbols so as to outputthe sequence of m symbols.
 20. The method as claimed in claim 19,wherein the puncturing is performed according to one of followingpuncturing patterns: {0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50,54, 57, 61} {0, 4, 8, 13, 16, 21, 25, 28, 32, 37, 43, 44, 49, 52, 56,62} {0, 4, 8, 13, 16, 21, 25, 31, 32, 37, 43, 44, 49, 52, 56, 61} {0, 4,8, 13, 18, 21, 25, 30, 35, 36, 40, 46, 50, 53, 57, 62} {0, 4, 8, 13, 18,21, 25, 30, 35, 37, 40, 47, 50, 53, 57, 62} {0, 4, 8, 13, 19, 22, 27,30, 33, 36, 41, 44, 49, 55, 58, 61} {0, 4, 8, 13, 19, 22, 27, 30, 33,36, 41, 44, 50, 52, 56, 63} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41,44, 50, 52, 58, 61} {0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50,54, 57, 61}
 21. A method for encoding k consecutive input bitsindicating a TFCI of each of successively transmitted frames into asequence of m48 coded symbols in an NB-TDD mobile communication system,comprising: continuously generating same symbols; creating firstsequences having a length m by puncturing a plurality of base orthogonalsequences; creating second sequences having a length m by puncturingbase mask sequences; multiplying the first sequences and the secondsequences by associated TFCI bits; and adding the resulting sequencescalculated by the multiplication and outputting the sequence of msymbols.
 22. The method as claimed in claim 21, wherein the baseorthogonal sequences include a 1^(st) Walsh code, a 2^(nd) Walsh code, a4^(th) Walsh code, an 8^(th) Walsh code, a 16^(th) Walsh code and a32^(nd) Walsh code, selected from orthogonal sequences of length
 64. 23.The method as claimed in claim 21, wherein the base mask sequencesinclude a 1^(st) mask sequence of0011010101101111101000110000011011110110010100111001111111000101, a2^(nd) mask sequence of0100011111010001111011010111101101111011000100101101000110111000, and a4^(th) mask sequence of0001100011100111110101001101010010111101101111010111000110001110. 24.The method as claimed in claim 21, wherein the predetermined puncturingpattern is one of following puncturing patterns: {0, 4, 8, 13, 16, 20,27, 31, 34, 38, 41, 44, 50, 54, 57, 61} {0, 4, 8, 13, 16, 21, 25, 28,32, 37, 43, 44, 49, 52, 56, 62} {0, 4, 8, 13, 16, 21, 25, 31, 32, 37,43, 44, 49, 52, 56, 61} {0, 4, 8, 13, 18, 21, 25, 30, 35, 36, 40, 46,50, 53, 57, 62} {0, 4, 8, 13, 18, 21, 25, 30, 35, 37, 40, 47, 50, 53,57, 62} {0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 49, 55, 58, 61}{0, 4, 8, 13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 56, 63} {0, 4, 8,13, 19, 22, 27, 30, 33, 36, 41, 44, 50, 52, 58, 61} {0, 4, 8, 13, 16,20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}
 25. An apparatus forencoding 10 consecutive input bits indicating a TFCI of each ofsuccessively transmitted frames into a sequence of 48 symbols in anNB-TDD mobile communication system, comprising: a (64, 10) second orderReed Muller code generator for generating 64 coded symbols by usinglength 64 Walsh codes and length 64 masks in response to the input bits;and a puncturer for puncturing 16 symbols out of the 64 coded symbolswherein puncturing positions of the 16 symbols are as follows; {0, 4, 8,13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}.
 26. An apparatusfor encoding 10 consecutive input bits indicating a TFCI of each ofsuccessively transmitted frames into a sequence of 48 symbols in anNB-TDD mobile communication system, comprising: a (48, 10) codegenerator for generating 48 coded symbols by using length 48 codes whichare punctured codes of length 64 Walsh codes and length 48 masks whichare punctured codes of length 64 masks, wherein the punctured codes oflength 64 Walsh codes and masks are a set of codes generated bypuncturing following positions out of the length 64 Walsh codes andmasks; {0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}.27. A method for encoding 10 consecutive input bits indicating a TFCI ofeach of successively transmitted frames into a sequence of 48 codedsymbols in an NB-TDD mobile communication system, comprising: creatingfirst sequences having a length 48 punctured orthogonal sequences;creating second sequences having a length 48 punctured mask sequences;multiplying the first sequences with each associated TFCI bit and thesecond sequences with each associated TFCI bit; and adding eachresulting sequences calculated by the multiplication and outputting thesequence of 48 symbols, wherein the punctured orthogonal sequences andthe punctured mask sequences are sequences generated by puncturingfollowing positions out of length 64 Walsh codes and length 64 masks;{0, 4, 8, 13, 16, 20, 27, 31, 34, 38, 41, 44, 50, 54, 57, 61}.